Method for improving cutting quality of super-thick multi-layer co-fired ceramic substrate grinding wheel

Abstract

A method for improving the quality of abrasive wheel cutting of ultra-thick multilayer co-fired ceramic substrates, belonging to the field of electronic components, is disclosed. The method involves: separating interconnected metal layers and retracting them inwards by a certain distance so that they are not touched during cutting; fabricating an ultra-thick substrate by mechanically or laser-drilling, filling, or screen printing on a green ceramic sheet; simultaneously coating both sides of the substrate to be cut with sealing wax for protection and adhering it to a ceramic pad; during cutting alignment, ensuring the cutting lines at both ends are on the same horizontal plane, using the center point as a reference, and performing vertical cutting using a multi-blade cut; after cutting, immersing the product in anhydrous ethanol until the substrate detaches from the pad, then repeatedly washing with anhydrous ethanol and deionized water, and drying for later use. This method solves the quality problems encountered in existing abrasive wheel cutting of ultra-thick multilayer co-fired ceramic substrates and has wide applications in the cutting of ultra-thick circuit boards.

Description

Technical Field

[0001] This invention belongs to the field of electronic components, and more specifically to the field of multilayer co-fired ceramic substrates. In particular, it relates to a method for improving the quality of grinding wheel cutting of ultra-thick multilayer co-fired ceramic substrates. Background Technology

[0002] Multilayer co-fired ceramic substrates (including LTCC and HTCC substrates) are an advanced high-density circuit packaging substrate. Through cavity design, microfluidic structure design, thermal design, and high-frequency performance design, they can achieve product miniaturization and high-frequency operation while providing excellent support and protection for resistors, capacitors, inductors, ceramic circuit boards and materials, and chips. They can be applied to various high-frequency, high-speed, and high-reliability integrated, miniaturized, and lightweight circuits. However, the substrate manufacturing process is complex, and the shrinkage rate is inconsistent, posing a significant challenge to the quality of abrasive wheel cutting.

[0003] Abrasive wheel cutting is widely used in the microelectronics industry for cutting hard and brittle materials due to its high efficiency, variety of tool types, and processes. However, when the thickness of the substrate being cut exceeds the cutting thickness of conventional products (greater than or equal to 3mm), the following problems will occur when using conventional cutting processes: (1) after cutting, the metal layer in the gold wire bonding area of ​​the substrate will curl or peel off; (2) after cutting, the metal layer on the front and back of the product will chip or lack gold; (3) after cutting, the metal layer of the internal through holes on the side of the substrate will be exposed; (4) quality problems such as low quality consistency, low reliability, and large potential hidden dangers. Due to its own nature, the circuit board cannot be used independently as a component and must rely on the packaging shell. The circuit board and the packaging shell need to be reliably interconnected to ensure that its function is protected and realized under harsh usage conditions. This places extremely strict requirements on the appearance and performance of the circuit board. The above phenomena greatly affect the appearance and performance of the substrate and directly lead to product scrap. Therefore, how to improve the quality of the product when the circuit board is cut is an important issue.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The technical problem to be solved by this invention is to solve the quality problems that occur when cutting ultra-thick multilayer co-fired ceramic substrates with a thickness greater than 3mm using existing grinding wheels, such as metal layer curling, peeling, chipping, missing gold, exposed metal layer in substrate through holes, substrate damage, low quality consistency, low reliability, and large potential hidden dangers.

[0006] Therefore, this invention provides a method for improving the cutting quality of ultra-thick multilayer co-fired ceramic substrates using abrasive wheels, such as... Figure 1-4 As shown.

[0007] Includes the following steps:

[0008] 1. Optimization of PCB layout design: The interconnected metal layers are changed to a separate state. Without affecting the internal wiring of the substrate, the metal layers are recessed inward by a certain distance to ensure that the cutting blade does not touch the metal layers during cutting, thus avoiding damage to the metal layers.

[0009] 2. Substrate fabrication: The substrate is fabricated by mechanically or laser drilling, filling, screen printing (with optimized design patterns), lamination, and sintering the raw ceramic sheet, followed by electroplating. The thickness of the fabricated substrate is greater than 3mm.

[0010] 3. Cutting process optimization:

[0011] (1) Protection of the front and back of the substrate: The front and back of the substrate to be cut are coated with sealing wax for protection and adhered to the ceramic pad to reduce the tearing of the metal layer by the shearing force. The sealing wax should not cover the reserved cutting lines and surface markings around the substrate.

[0012] The sealing wax is prepared by mixing shellac flakes, calcium oxide and rosin in a ratio of 1:1:1 to 1:1:3. The sealing wax melts at a temperature of 140 to 150°C and can automatically detach without residue after being boiled in alcohol at 150°C for 30 minutes.

[0013] (2) Cutting alignment: When cutting and aligning, each row of products should first ensure that the cutting lines on the left and right ends are on the same horizontal plane. Then, the center point position marked on the upper and lower parts of the substrate surface should be used as a reference for cutting to ensure the cutting accuracy and avoid the cutting offset of the internal through holes and metal layers on the side, which may result in exposure.

[0014] (3) Cutting method: The number of cutting blades has been changed from the previous single cut to multiple cuts to minimize the left and right wobbling of the blade wheel inside the product during cutting, which would affect the perpendicularity of the product edge or cause the blade to break. At the same time, the shearing force of the blade wheel on the front and back metal layers is reduced to the minimum.

[0015] 4. Cleaning: After cutting, put the product into a beaker and heat it with anhydrous ethanol until the substrate product is separated from the gasket. Then clean it repeatedly with anhydrous ethanol and deionized water, and dry it.

[0016] Beneficial effects of this invention:

[0017] This invention solves the defects in the metal layer caused by cutting ultra-thick multilayer ceramic substrates (thickness greater than 3.3mm) through structural design optimization and cutting process optimization, such as edge curling, edge chipping, missing gold, and exposed metal layer of internal through holes on the side. It improves the appearance quality of the substrate after cutting and the yield rate of substrate production.

[0018] The method of this invention is simple, easy to implement, and low in cost, and is suitable for cutting ultra-thick multilayer circuit boards of various shapes. Attached Figure Description

[0019] Figure 1 A schematic diagram comparing the structure of the bridge design before and after optimization.

[0020] Figure 2 Schematic diagram of LTCC substrate-bridge pad and substrate coated with sealing wax structure.

[0021] Figure 3 Schematic diagram of the cutting lines at both ends of the LTCC substrate-bridge.

[0022] Figure 4 Schematic diagram showing the center positions of the upper and lower through holes on the surface of the LTCC substrate-bridge circuit.

[0023] In the figure: 1a is the inner layer metal PCB design of the bridge before optimization, 1b is the inner layer metal PCB design of the bridge after optimization, 2a is the aluminum nitride ceramic pad coated with sealing wax, 2b is the LTCC substrate product coated with sealing wax on both sides and then mounted on the aluminum nitride ceramic pad, 3a is the center line of the cut at the left and right ends, and 3b is the cut range line at the left and right ends. Detailed Implementation

[0024] like Figure 1-4 As shown, taking the LTCC low-temperature multilayer co-fired ceramic substrate of the bridge as an example, the specific implementation method of the method for improving the grinding wheel cutting quality of ultra-thick multilayer co-fired ceramic substrate is as follows:

[0025] 1. Optimization of the inner layer metal PCB design for LTCC substrate-bridge circuit:

[0026] The original fabric design drawing ( Figure 1 a) The internally interconnected metal layers (such as Figure 1 (As shown in A) Change to a separate state, such as Figure 1 As shown in B, without affecting the internal wiring of the substrate, the metal layer is recessed a certain distance to ensure that the cutting blade will not touch the metal layer during cutting, thus minimizing damage to the metal layer. The final layout design is optimized as follows: Figure 1 As shown in b.

[0027] 2. LTCC substrate-bridge fabrication: The circuit board is fabricated by mechanically drilling, filling, screen printing (with optimized design patterns), stacking, laminating and sintering processes on the green ceramic sheet. The thickness of the LTCC substrate-bridge is 3.3mm.

[0028] 3. Cutting process optimization:

[0029] (a) Protection of the front and back of the substrate: Place a 50mm×50mm×0.5mm aluminum nitride ceramic pad on a heating platform, set the heating platform temperature to 150℃, and then apply sealing wax to the ceramic pad (the area should be slightly larger than the substrate to be cut). After the sealing wax melts, place the LTCC substrate-bridge to be cut on the ceramic pad coated with sealing wax (front and back sides, graphic side up), and gently press it flat with stainless steel tweezers to ensure the substrate is completely adhered to the ceramic pad. Then apply sealing wax to the surface of the product, ensuring that the sealing wax does not cover the pre-reserved cutting lines around the product or the upper and lower markings on the substrate surface. Figure 2 As shown.

[0030] (b) Cutting Alignment: When aligning each row of products, prioritize ensuring that the cutting lines at both ends are on the same horizontal plane, such as... Figure 3 As shown. Then, using the center point of the two through holes on the top and bottom of the product as a reference, make the cut, as follows. Figure 4 As shown.

[0031] (c) Cutting method: A two-blade cut is used to minimize the left and right wobbling of the cutter wheel inside the product during cutting, which would affect the perpendicularity of the product edge, while minimizing the shearing force of the cutter wheel on the front and back metal layers.

[0032] 4. Cleaning: After cutting, place the ceramic gasket in a beaker and soak it in anhydrous ethanol. Place it on a heating platform and heat to 150℃ for 30 minutes until the product automatically detaches. Pour off the cloudy anhydrous ethanol, then pour anhydrous ethanol into the beaker to clean the product. After cleaning, pour anhydrous ethanol into the product again and heat it on the heating platform until the anhydrous ethanol boils. Pour off the anhydrous ethanol and wait for the remaining anhydrous ethanol in the beaker to completely evaporate. Rinse the product with deionized water repeatedly to remove any remaining solution (pour in and out repeatedly; it cannot be recycled). Rinse with deionized water at least three times. Finally, dry the product in an oven at 120℃~180℃ for 30 minutes to 2 hours, preferably at 150℃ for 1 hour.

[0033] Finally, it should be noted that the above embodiments are merely examples for clear illustration. This invention includes, but is not limited to, the above embodiments, and it is neither necessary nor possible to exhaustively describe all possible implementations. Those skilled in the art can make other variations or modifications based on the above description. All implementation schemes that meet the requirements of this invention are within the protection scope of this invention.

Claims

1. A method for improving the cutting quality of ultra-thick multilayer co-fired ceramic substrates using abrasive wheels, characterized in that, Includes the following steps: (1) Optimization of PCB design: The interconnected metal layers are changed to a separate state, and the metal layers are shrunk inward a certain distance so that they will not be touched during cutting. (2) Substrate fabrication: A substrate with a thickness greater than 3mm is fabricated by mechanical or laser drilling, hole filling, screen printing, lamination, and electroplating of the raw ceramic sheet. The substrate surface has pre-reserved cutting lines around the four sides and alignment cutting marks on both sides centered on the cutting lines. (3) Cutting process optimization: ① Protection of the front and back of the substrate: Apply sealing wax to both sides of the substrate to be cut for protection and adhere it to the ceramic pad. The sealing wax should not cover the reserved cutting lines and surface markings around the substrate. ② Cutting and alignment: When cutting and aligning, each row of products should first make the cutting lines on the left and right ends on the same horizontal plane, and then cut according to the center point position marked on the upper and lower parts of the substrate surface. ③ Cutting method: Use a multi-blade cutting method to make vertical cuts; (4) Cleaning process: After cutting, put the product into a beaker and heat it with anhydrous ethanol until the substrate product is removed from the gasket. Then clean it repeatedly with anhydrous ethanol and deionized water, and then dry it for later use. The sealing wax is made of shellac flakes, calcium oxide and rosin in a ratio of 1:1:1 to 1:1:

3. The sealing wax has a melting temperature of 140 to 150°C. It automatically detaches after being boiled in alcohol at 150°C for 30 minutes, leaving no residue.

2. The method for improving the cutting quality of ultra-thick multilayer co-fired ceramic substrates using abrasive wheels as described in claim 1, characterized in that: The substrate has a thickness of 3.3 mm.

3. The method for improving the cutting quality of ultra-thick multilayer co-fired ceramic substrates using abrasive wheels as described in claim 1, characterized in that: The substrate is a multilayer co-fired ceramic substrate.

4. The method for improving the cutting quality of ultra-thick multilayer co-fired ceramic substrates using a grinding wheel as described in claim 1, characterized in that: The multilayer co-fired ceramic substrate is an LTCC substrate or an LTCC substrate.

5. A method for improving the cutting quality of ultra-thick multilayer co-fired ceramic substrates using a grinding wheel as described in any one of claims 1-4, characterized in that... The protection of the front and back of the substrate is as follows: Place an aluminum nitride ceramic pad measuring 50mm×50mm×0.5mm on a heating platform, set the heating platform temperature to 150℃, then apply sealing wax to the ceramic pad. After the sealing wax melts, place the substrate to be cut on the sealing wax-coated ceramic pad with the substrate graphic side facing up, and gently press it flat to make the substrate completely adhere to the ceramic pad. Then apply sealing wax to the surface of the substrate, ensuring that the sealing wax does not cover the reserved cutting lines around the product or the upper and lower markings on the substrate surface.

6. The method for improving the cutting quality of ultra-thick multilayer co-fired ceramic substrates by abrasive wheel as described in claim 5, characterized in that... The area of ​​the sealing wax coated on the ceramic gasket is slightly larger than that of the substrate to be cut.

7. The method for improving the cutting quality of ultra-thick multilayer co-fired ceramic substrates by abrasive wheel as described in claim 1, characterized in that: The cutting method involves making a vertical cut using two cuts.

8. The method for improving the cutting quality of ultra-thick multilayer co-fired ceramic substrates by abrasive wheel as described in claim 1, characterized in that: The cleaning process is as follows: (1) After cutting, the ceramic gasket is placed in a beaker and soaked in anhydrous ethanol; (2) Then place it on a heating platform and heat it to 150℃ for 30 minutes, after which the product will automatically detach. (3) Pour off the turbid anhydrous ethanol, then pour anhydrous ethanol into the beaker to wash the product. (4) After cleaning, pour anhydrous ethanol into the product and place it on a heating platform to heat until the anhydrous ethanol boils. (5) Pour out the anhydrous ethanol and wait for the remaining anhydrous ethanol in the beaker to evaporate completely; (6) Clean the substrate with the protective layer removed repeatedly with deionized water to remove the residual solution on the product. Clean with deionized water more than three times. (7) Dry in an oven.

9. The method for improving the cutting quality of ultra-thick multilayer co-fired ceramic substrates using abrasive wheels as described in claim 8, characterized in that: The drying conditions are: 120℃~180℃, 30 minutes~2 hours.

10. The method for improving the cutting quality of ultra-thick multilayer co-fired ceramic substrates using abrasive wheels as described in claim 9, characterized in that: The drying conditions are: 150℃ for 1 hour.

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